This invention relates to a hand-held appliance for personal hygiene, in particular for tooth and mouth care. The appliance is of the type having a grip portion for locating a spray nozzle, the grip portion being provided with an actuating device with a manipulating element for adjusting the flow-rate of a pinch valve provided in the interior of the shell of the hand-held appliance. The hand-held appliance also includes a shut-off device for temporarily interrupting the flow by actuating the same pinch valve without changing the setting of the flow-rate. A hand-held appliance of this kind is for instance described in the prior West German Patent Application No. P 33 47 239.4.
With hand-held appliances of this kind, for instance mouth spray units or oral irrigating appliances used in dentistry, it is essential to be able to set the flow-rate and to temporarily interrupt the flow. This requirement is fulfilled in an oral irrigating appliance used in dentistry, as disclosed in EP-OS No. 0 023 672, which has an actuating ring capable of being turned on a grip portion with the position of the actuating ring governing the extent to which a ball acting as a squeezing element is pressed against a tube to be squeezed off via inclined surfaces. With this appliance the inclined surfaces in the actuating ring are designed in relation to the ball and the other component parts in such a manner that when the actuating ring is in one terminal position, the tube is not squeezed off, and with the actuating ring in another terminal position, it is completely squeezed off.
The hand-held appliance just mentioned has the shortcoming that the actuating ring remains in the position that leads to an interruption of the flow when released. This can result in the pump that delivers the water through the hand-held appliance remaining switched on, without any given necessity, for a prolonged duration of time without being capable of delivering water through the hand-held appliance. For mains-operated mouth spray units the pump motor will be designed in such a manner that the water pressure built up during interrupting the flow through the hand-held appliance is allowed to rise to such an extent that a bypass opens in the pump. In this case the pump produces a noise that is above that present during normal operation. Hence, the user is reminded to switch off the pump. The situation with battery-operated mouth spray units is, however, different in the majority of cases. At least when the battery-operated mouth spray units are set to low water pressure, current keeps flowing through the pump motor when the water flow is interrupted at the hand-held appliance. Hence, it can easily be forgotten to switch off the pump after an interruption of the water flow, resulting in the battery quickly becoming discharged and in the pump motor possibly being damaged or destroyed.
A further shortcoming of the hand-held appliance previously known according to EP-OS No. 0 023 672 rests with the desired flow-rate having to be reset after interrupting the flow. Therefore, the flow-rate setting deemed optimal at one given moment is cancelled with each interruption of the flow.
The shortcoming mentioned last is avoided in the hand-held appliance designed as a mouth-spray unit according to the German Patent Application No. P 33 47 239.4 mentioned at the beginning in that an actuating ring is provided which is capable of being shifted in the longitudinal direction of the grip portion for interrupting the flow and in that the actuating ring is capable of being turned independently thereof for adjusting the flow rate. This provision ensures that the selected flow-rate setting remains unchanged after an interruption of the flow.
The frictional forces that have to be surmounted in order to shift the actuating ring for purposes of interrupting the water flow, are, however, invariably so high that the actuating ring is only capable of automatically returning into a position that allows the water to flow again after an interruption of the flow and after releasing said actuating ring when provision is made of an additional pull-back spring. Such sophistication has, however, become inadequate for most hand-held appliances and automatically renders them susceptible to failure.